The invention relates generally to medical equipment used in the surgical treatment of disease, and more particularly to a system and method for medical instrument navigation by optically tracking the positions of instruments used during surgery or other treatments in relation to a patient""s anatomy.
Image guided stereotaxy is widely used in the field of neurosurgery. It involves the quantitative determination of anatomical positions based on scan data taken from a CT, MRI or other scanning procedures to obtain three-dimensional scan data. Typically, the image scan data is placed in a computer to provide a three-dimensional database that may be variously used to provide graphic information. Essentially, such information is useful in surgical procedures and enables viewing a patient""s anatomy in a graphics display.
The use of image guided stereotactic head frames is commonplace. For example, see U.S. Pat. No. 4,608,977 issued Sep. 2, 1986 and entitled, System Using Computed Tomography as for Selective Body Treatment. Such structures employ a head fixation device typically with some form of indexing to acquire referenced data representative of scan slices through the head. The scan data so acquired is quantified relative to the head frame to identify individual slices. A probe or surgical instrument may then be directed to an anatomical feature in the head by mechanical connection to the head frame based on scan data representations. Three-dimensional scan data has been employed to relate positions in a patient""s anatomy to other structures so as to provide a composite graphics display. For example, a mechanically linked space pointer (analogous to a pencil) attached to the end of an encoded mechanical linkage might be directed at a patient""s anatomy and its position quantified relative to the stereotactic scan data. The space pointer might be oriented to point at an anatomical target and so displayed using computer graphics techniques. Such apparatus has been proposed, using an articulated space pointer with a mechanical linkage. In that regard, see an article entitled xe2x80x9cAn Articulated Neurosurgical Navigational System Using MRI and CT Images,xe2x80x9d IEEE Transactions on Biomedical Engineering, Volume 35, No. Feb. 2, 1988 (Kosugi, et al.) incorporated by reference herein.
The above-described systems have at least two disadvantages of note. First, the head frame and the articulated space pointer are mechanically connected to an apparatus used to measure and calculate the position of the probe or pointer. Consequently, although a relatively high number of degrees of freedom can be provided to the pointer (or other tool coupled to the pointer), the mechanical linkage may still restrict the possible ranges of motion available to the clinician. Furthermore, the linkages may be large and obtrusive, and can be difficult to sterilize.
Second, although the apparatus tracks the position of the space pointer in relation to the patient""s anatomy, the clinician is still free to move about the patient and operate from any desired position. This is not reflected by the data produced by the device. Accordingly, although a xe2x80x9cpointer""s eyexe2x80x9d view of the surgical field can be provided, if the clinician is operating from any of various other angles, then any graphical representation of the surgical field may be disorienting, confusing, or not representative of the xe2x80x9csurgeon""s eyexe2x80x9d view. Although the system""s point-of-view might be selected and altered manually, this is not an optimum solution, as it requires additional steps to be taken by the clinician or an assistant.
In light of the above considerations, the need for relating external treatment apparatus or surgical viewing directions to a specific target arises in several aspects. For example, the need arises in relation to the treatment of internal anatomical targets, specifically to position and maintain such targets with respect to a surgical instrument such as a probe, a microscope with a specific direction and orientation of view, or an X-ray treatment beam associated with a large external apparatus. Thus, a need exists for methods for aligning a surgical instrument, probe, or beam not attached by any mechanical linkage, to impact specific anatomical targets via a path selected to avoid injury to other critical anatomical structures. A further need exists for the capability to show the operating clinician a view of the patient""s anatomy and the surgical tool from a perspective that is natural to the clinician, and not disorienting or confusing. Further, there is a need for an economic, compact, and wireless system and method to track instruments in clinical applications.
Generally, in accordance herewith, an optical camera apparatus functions in cooperation with a computer system and a specially configured surgical instrument. In an embodiment of the invention, the camera system is positioned to detect a clinical field of view and to detect index markers on a surgical instrument, a patient, and/or a surgeon. The markers are tracked by the camera apparatus. The image scan data (such as from a CT or MR scan of the patient""s anatomy) and data specifying the position of the instrument and the surgeon are transformed relative to the patient""s anatomy and the camera coordinate system, thereby aligning the scan data, patient position and orientation data, instrument position and orientation data, and surgeon position and orientation data for selectable simultaneous viewing on a computer display.
Various exemplary embodiments are given of the use of lines, arrays of points, geometric patterns and figures, lines of light, and other optically detectable marker configurations to identify the position and orientation of a surgical instrument, a patient, and a surgeon. The disclosed embodiments have the advantage of being wireless and optically coupled to the camera tracking system. Moreover, they can be relatively economical and lightweight in comparison to the mechanically coupled tracking devices described in the background section above. Once the positions of the instrument, patient, and surgeon have been determined with respect to a common coordinate system, a simulated view of the instrument and the patient can be provided on a display device in a manner that is comfortable and convenient to the surgeon. In an embodiment of the invention, the simulated view is overlaid with an actual live video display to further orient the surgeon.